1. Field of the Invention
The present invention is concerned with a dental wrench. In particular, it is concerned with a bifunctional dental wrench which is utilized to engage and disengage a dental bur or other operative tool from the collet of a dental handpiece and to secure or remove a threaded end cap to the housing of a turbine cartridge assembly of the dental handpiece.
2. State of the Art
Various dental collet or chuck wrenches have been described in the art. Typically, such wrenches are mono-functional in that they are adapted to adjust a collet or chuck of a dental handpiece for engagement or disengagement with a dental bur or similar dental tool. Representative of the mono-functional dental wrenches are those described in U.S. Pat. Nos. 3,960,039; 3,888,008; 3,935,761; 3,947,966; and 4,033,040.
A dental wrench which utilizes a collet engaging tool and a turbine assembly housing end cap engaging tool is known in the art and is described in U.S. Patent Application Ser. No. 947,216, filed Sept. 29, 1978.
A problem associated with the prior art wrench has been the difficulty of applying sufficient torque to the end cap of the turbine housing on the dental handpiece such that the end cap does not loosen during operation of the handpiece. The small diameter rotatable knob on which is mounted the drive means to engage or disengage the end cap makes the application of sufficient torque to the end cap difficult since the resultant moment arm is small. It is generally not desirable to enlarge the diameter of the knob since the knob also is connected to the shaft which adjusts the collet or chuck mechanism for engaging or disengaging a dental bur or other tool. Application of excessive torque to the collet assembly can strip the threaded portions of the assembly and render it inoperative.
Accordingly, there is a need for a single dental wrench assembly which is bifunctional, so that it is possible to adjust the collet or chuck assemby of a handpiece and also engage or disengage the end cap on the turbine housing. It is also desirable to have a wrench which is constructed to permit application of greater torque when engaging the end cap with the housing of handpiece then when the collet assembly is being adjusted.